Related Field
Various embodiments of the present invention relates to a method for welding a workpiece and a method for forming a three-dimensional article. Associated apparatuses and computer program products are also provided.
Description of Related Art
Freeform fabrication or additive manufacturing is a method for forming three-dimensional articles through successive fusion of chosen parts of powder layers applied to a worktable. A method and apparatus according to this technique is disclosed in US 2009/0152771.
Such an apparatus may comprise a work table on which the three-dimensional article is to be formed, a powder dispenser, arranged to lay down a thin layer of powder on the work table for the formation of a powder bed, a ray gun for delivering energy to the powder whereby fusion of the powder takes place, elements for control of the ray given off by the ray gun over the powder bed for the formation of a cross section of the three-dimensional article through fusion of parts of the powder bed, and a controlling computer, in which information is stored concerning consecutive cross sections of the three-dimensional article. A three-dimensional article is formed through consecutive fusions of consecutively formed cross sections of powder layers, successively laid down by the powder dispenser.
There is always a demand for decreasing or minimizing the time for fusing powder material in additive manufacturing or when welding pieces together. One way to increase the efficiency and the speed in AM or when welding in general is to increase the power of the energy beam and at the same time increase the speed of deflection of said energy beam. The deposited power per surface unit can thereby be kept constant but being distributed faster over the surface which is to be fused or welded. However, this only works until a predetermined power and speed of deflection of said energy beam. If increasing the power over a predetermined value, the speed of deflection will be too fast so that the heat from the energy beam will not have sufficient time to penetrate into the material to be fused or welded. With a too high power and thereby a too fast speed of deflection of said energy beam, the surface temperature will become too high so that the material which is to be fused or welded is instead evaporated.
There is a need in the art to beyond that predetermined power and speed of deflection in welding and without evaporating the material which is to be fused or welded.